Emerson Process Management FISHER 657 - Manual (Page 10)

Instruction Manual
D100306X012
657 Actuator (30-70 and 87)
December 2010
10
Loading Connection
The loading pressure connections are made at the factory if the valve, actuator, and positioner come as a unit. Keep
the length of tubing or piping as short as possible to avoid transmission lag in the control signal. If a volume booster,
valve positioner or other accessory is used, be sure that it is properly connected to the actuator. Refer to the positioner
instruction manual or other manuals as necessary.
For actuators shipped separately or whenever the actuator pressure connections are installed, use the following steps:
1. Connect the loading pressure piping to the NPT internal connection in the top of the diaphragm casing.
2. For sizes 70 and 87 actuators, if necessary, remove the 1/4 NPT bushing if a 1/2 NPT internal connection is needed
to increase connection size. The connection can be made with either piping or tubing.
3. Cycle the actuator several times to be sure that the valve stem travel is correct when the correct pressure ranges
are applied to the diaphragm.
WARNING
If valve stem travel appears to be incorrect, refer to the Bench Set Spring Adjustment procedures at the beginning of this
section. To avoid personal injury or product damage, do not place the valve into service if it is not reacting correctly to
diaphragm loading pressure changes.
Maintenance
Actuator parts are subject to normal wear and must be inspected and replaced when necessary. The frequency of
inspection and replacement depends on the severity of service conditions.
WARNING
Avoid personal injury or property damage from sudden release of process pressure or bursting of parts. Before performing
any maintenance operations:
D Do not remove the actuator from the valve while the valve is still pressurized.
D Always wear protective gloves, clothing, and eyewear when performing any maintenance operations to avoid personal
injury.
D Disconnect any operating lines providing air pressure, electric power, or a control signal to the actuator. Be sure the
actuator cannot suddenly open or close the valve.
D Use bypass valves or completely shut off the process to isolate the valve from process pressure. Relieve process pressure
from both sides of the valve. Drain the process media from both sides of the valve.
D Vent the power actuator loading pressure and relieve any actuator spring precompression.
D Use lock‐out procedures to be sure that the above measures stay in effect while you work on the equipment.
D The valve packing box may contain process fluids that are pressurized, even when the valve has been removed from the
pipeline. Process fluids may spray out under pressure when removing the packing hardware or packing rings, or when
loosening the packing box pipe plug.
D Check with your process or safety engineer for any additional measures that must be taken to protect against process
media.